/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.truth.Truth.assertThat;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertFalse;
import static junit.framework.Assert.assertTrue;
import static junit.framework.Assert.fail;

import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import javax.annotation.CheckForNull;

/**
 * Used to test listenable future implementations.
 *
 * @author Sven Mawson
 */
public class ListenableFutureTester
{

    private final ExecutorService exec;
    private final ListenableFuture<?> future;
    private final CountDownLatch latch;

    public ListenableFutureTester(ListenableFuture<?> future)
    {
        this.exec = Executors.newCachedThreadPool();
        this.future = checkNotNull(future);
        this.latch = new CountDownLatch(1);
    }

    public void setUp()
    {
        future.addListener(
                new Runnable()
                {
                    @Override
                    public void run()
                    {
                        latch.countDown();
                    }
                },
                exec);

        assertEquals(1, latch.getCount());
        assertFalse(future.isDone());
        assertFalse(future.isCancelled());
    }

    public void tearDown()
    {
        exec.shutdown();
    }

    public void testCompletedFuture(@CheckForNull Object expectedValue)
            throws InterruptedException, ExecutionException
    {
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertEquals(expectedValue, future.get());
    }

    public void testCancelledFuture() throws InterruptedException, ExecutionException
    {
        assertTrue(future.isDone());
        assertTrue(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertTrue(future.isCancelled());

        try
        {
            future.get();
            fail("Future should throw CancellationException on cancel.");
        }
        catch (CancellationException expected)
        {
        }
    }

    public void testFailedFuture(@CheckForNull String message) throws InterruptedException
    {
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        assertTrue(latch.await(5, TimeUnit.SECONDS));
        assertTrue(future.isDone());
        assertFalse(future.isCancelled());

        try
        {
            future.get();
            fail("Future should rethrow the exception.");
        }
        catch (ExecutionException e)
        {
            assertThat(e).hasCauseThat().hasMessageThat().isEqualTo(message);
        }
    }
}
